Impact of human activities on organic carbon transport in the Yellow River

Abstract

Using data from four field investigations between 2003 and 2009 along the Yellow River mainstream, we examined the transport features and seasonal variations of organic carbon, with a focus on contrasting the impacts of human activities with those of natural processes. Particulate organic carbon (POC) in the Yellow River originated mainly from the Loess Plateau, and thus the POC content in suspended sediments was much lower than in the world's other large rivers. Owing to both natural and human influences, dissolved organic carbon (DOC) has only a weak correlation with discharge. DOC varied as a result of human activities such as agricultural irrigation and pollution in the whole basin except for the upstream Qinghai–Tibetan Plateau. Our study also suggested that while reservoirs are a POC sink over short periods, a long-term POC storage flux cannot be easily estimated as discharge and sediment regulations have completely changed the relationship between the fluxes of water, sediments, and rainfall. However, this carbon sink can be obtained reliably through high-frequency sampling over long time periods. In addition, the annual water and sediment regulation (WSR) scheme has imposed an extremely severe human disturbance on the transport pattern of river organic carbon. Our study demonstrated for the first time that in a WSR event of less than 20 days, large proportions of the annual DOC (35%) and POC (56%) fluxes of the Yellow River were transported to the estuarine and coastal zone, potentially influencing estuarine and coastal geochemistry and ecosystems profoundly

Impact of Wetland Decline on Decreasing Dissolved Organic Carbon Concentrations along the Mississippi River Continuum

“…Most rivers showed no obvious gradients or features (e.g., Lena; Lara et al, 1998, Columbia;Prahl et al, 1998, Paraná;Depetris and Kempe, 1993, and Yellow;Zhang et al, 2013), while other rivers displayed an increase or decrease only in a river section (e.g., Yangtze; Wu et al, 2007;Zhang et al, 2014 and Colorado;Miller, 2012). Consistent downstream increases occurred in the Amazon River (Hedges et al, 2000) and the St. Lawrence below the Great Lakes (Massicotte and Frenette, 2011).…”

Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems: Concepts, emerging trends, and research challenges

“…More than 110,000 silt check dams have been constructed in the Loess Plateau since the 1950s, trapping approximately 21 billion tons of sediment in the reservoirs (Zhang et al, 2016). A conservative estimate indicates that the rate of annual POC trapping in more than 3,000 large dams (excluding 110,000 silt check dams) within the Yellow River basin can amount to 3.34.3 Tg C yr −1 (1 Tg 255 =10 12 g; Zhang et al, 2013;Ran et al, 2014), which is similar in magnitude to the total organic C export to the Bohai Sea (4.1 Tg C yr −1 ; Ran et al, 2014;Fig. 3).…”

“…While POC trapped in the reservoir sediments has been considered as a relatively stable C sink (Zhang et al, 2013) of POC and DOC in the increasingly impounded rivers across Asia (Sarma et al, 2011). As illustrated by the relatively high rate (27%) of CO2 emission from the POC eroded from the entire Yellow River basin (Ran et al, 2014;Fig.…”

Sources and preservation of sedimentary organic matter in the Southern Bohai Sea and the Yellow Sea: Evidence from lipid biomarkers

“…The TOC inputs to NYS and SYS were estimated only to be 32 ton/km 2 /yr and 25 ton/km 2 /yr, respectively. Annually in 2000-2008, the Yellow River transported about 430,000 ton of OC to the sea (Zhang et al, 2013). In comparison, the Yellow River OM discharge is the important source of TOM to the shelf, and the discharged TOM is mostly trapped in SBS (Fig.…”

“…On hand, large amounts of TOM are annually transported from the continent to the ocean with the Yellow River-derived sediment transport. It was estimated that sediment discharge from the Yellow River to the sea (approximately 1 Â 10 9 ton/yr) was the second largest input from a single river worldwide, and the total organic carbon discharge accounted for 1% of total organic carbon transported by rivers into ocean worldwide in history (before 1990) (Zhang et al, 2013). On the other hand, due to the transport and deposition of riverderived fine-grained sediments are controlled by estuarine processes, tidal currents, shelf circulation and episodic storm, those fine-grained sediments accumulate in the central areas of open sea and form isolated mud patches (Alexander et al, 1991;Lim et al, 2007).…”